In the never-ending search for more power, superchargers and turbochargers have a lot to offer, but which is the preferred form of boost?
Since the beginnings of the combustion engine, achieving more power has been a consistent and overriding goal. Two popular ways of getting additional engine output are the turbocharger and the supercharger. Both feed additional air, and therefore oxygen, into an engine. The more air fed into the combustion chamber, along with the fuel, the bigger the bang.
Many have called our current automotive era, with its Hellcats and biturbo V8s, the peak of internal combustion. Indeed, in this liminal, proto-electrification moment, we find some of the most impressive cars ever made, boasting absurd horsepower and torque ratings, get their peak power via turbocharging or supercharging.
But before we get to which is “better,” let’s take a moment to appreciate their different approaches to the same goal, more power.
Though their primary function is similar, turbochargers and superchargers go about providing boost in different ways. Both use an impeller to force air into the combustion chamber, but they diverge in how they power that impeller.
The turbocharger is made up of a single shaft with two turbines/impellers on each end. One end is the hot side of the turbo while the other end is the cold side. On the hot side of the turbo, its turbine is spun by exhaust gases leaving the engine. The force of those exiting gases spins the turbine’s shaft. On the other end of that shaft is the cold side of the turbo which sucks in cold air and forces it into the combustion chamber. More air, more bang, more power.
The supercharger differs from the turbocharger in that it isn’t spun by exhaust gases but instead is directly spun either by a belt attached to the motor itself or by a separate electric motor. There are also different kinds of superchargers. Route and twin-screw superchargers feature two lobed rotors which spin and compress air which is then sent into an intercooler before being fed into the combustion chamber. Centrifugal superchargers feature a turbine similar to those found in a turbocharger but is driven by a belt connected to the engine. An electric supercharger is similar in design to a centrifugal one except that it is driven by a separate electric motor, often with its own alternator and battery.
Turbochargers and supercharger both have their own unique pros and cons. For turbochargers, their benefits lie in their efficiency. Pirating exhaust gases means turbos don’t demand additional energy from the system. They’re a net gain in output. Turbochargers also can provide total boost when compared to superchargers, for reasons we’ll get to in a moment.
The downsides of turbos are that they are fairly complex. It’s that complexity that has some Ford EcoBoost owners bemoaning the engines as problematic. Another downside arises from the fundamental turbocharger design. Because a turbo is spun from exhaust gases, those gases and the pressure necessary to spin the turbo need to build up in the system. This creates a delay between throttle application and subsequent boost. This is what’s known as turbo lag. (Dun, dun, DUN!!!)
One of the key benefits of a supercharger is that it doesn’t have a lag. Because the supercharger, whether belt driven or motorized, has power being directly applied to it, it can provide boost immediately. In the case of route and twin-scroll superchargers, boost is provided across a wide spectrum of the rev range (unlike a turbo, which needs to reach a certain boost threshold before providing additional power).
The principal downside of superchargers is that they are inefficient. Because they take mechanical energy from the engine, the system overall becomes less efficient. You can get plenty of boost, but it will cost you in fuel and emissions. Another downside of superchargers is their size. While not as complex as turbochargers, superchargers tend to be big which makes them harder to fit into tight engine bays. Something of particular concern for those looking to boost a naturally aspirated engine.
Obviously, both turbochargers and superchargers can be great ways to coax extra power from an engine, but which is better? The answer depends on who you are.
For automotive manufacturers, the turbocharger has been the preferred method for boosting output. Thanks to modern turbos, automakers have been able to replicate the power of larger engines with smaller ones. V6s have transformed into turbo inline fours. V8 have been swapped out for turbo V6s in performance cars, take the Kia Stinger and its twin-turbo V6 for instance. Not only has turbocharging helped manufacturers meet government mandated emissions targets, but it has also given a power boost to less expensive commuter cars, traditionally laggards. Thanks to modern turbos, these cars can now often boast close to 200 horsepower, and sometimes much more.
And yet, superchargers do offer some significant advantages over turbochargers. The lack of any lag is foremost. Though some might fetichize that delayed turbo kick, many enthusiasts prefer the smoothness and immediacy of a supercharger’s boost. And then there’s the simplicity of a supercharger in comparison to a turbocharger. The added lifetime expenses of fixing a turbocharged engine are an avoidable headache if you go the supercharger route.
So, which is better? On the whole, turbos have been better for the environment and an overall improvement for the average driving experience. But if you’re seeking a boost for your current project car, we’d suggest strongly considering going with a supercharger.